My little race bike

GoldenMotor.com

Skyking

New Member
Aug 22, 2014
106
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North Central Texas
I thought that I should post some info, and a picture on my current build. This is an old full suspension BMX bike that I picked up many years ago. I'm waiting on KC Vales new kit to mount the engine, and drive. It has a Bendix coaster brake hub on the back, and a Bendix hub on the front. The forks, and shocks are mainly just spring damping, but they do have a little bit of air compression damping also.
I've got a set of Hutchinson GP1 race tires ordered, and will mount them and true the wheels at the same time.
I plan on putting a disc brake on the front.
I need to cut down the handle bars, or I may put on a set of clamp-ones.
I set the tank, and seat on to see how they look. I need to get the seat upholstered, and figure out how to mount the tank. I'm going to move the petcock bung to the rear, bottom of the tank.
I haven't decided on which motor I'll put in it, but I'm leaning towards my fully modded Chung Yang GP460. It's a very strong, and light weight motor, that should fit well into the limited space that is available. It's fully reed ported with a DDM Dominator side bleed tuned pipe, and a 19mm diaphragm Walbro carb on it. I have not had it on a dyno, but I'm putting it in the 9 to 10 HP range, and 14,000+ RPM's.
More info to come as the build progresses.
 

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2door

Moderator
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Sep 15, 2008
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Very unique and interesting bike, Sky. Keep us informed on the progress of this build.

There are some some intriguing features about the frame that gives it an unusual look. It's certainly not something we see every day.

Tom
 

Davezilla

New Member
Mar 15, 2014
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Definitely unique and will make for a really cool build too...
That would be a good platform to put that Morini engine you got in, it would be a tight fit but it would make for a cool looking bike that could do around 50mph or so...
 

bairdco

a guy who makes cool bikes
Aug 18, 2009
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living the dream in southern california
Haven't seen one of those for a while. The "silver fox," I think. Big heavy bmx bike that was about the worst race bike if you wanted to race it or jump it, cuz they weighed a ton.

Should make a cool motorized bike, tho.
 

Skyking

New Member
Aug 22, 2014
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North Central Texas
Haven't seen one of those for a while. The "silver fox," I think. Big heavy bmx bike that was about the worst race bike if you wanted to race it or jump it, cuz they weighed a ton.

Should make a cool motorized bike, tho.
Big; no. Those are 16" wheels. Heavy; kinda. I haven't weighed it, but what you see pictured is around 40lbs. It is Very sturdy.

Dave; I don't think the Morini will fit. I'm going to have to shoe spoon the GP460 into it.
 

Skyking

New Member
Aug 22, 2014
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North Central Texas
UPDATE: Tires, tubes, and rim strips came today. Mounted, and only one pinch flat. Very soft, and sticky. Should really hold the track, and won't last 500 miles. They're directional. "H" rated. Ambitious? Maybe, maybe not.
Stay tuned............
Oh, and I mounted a better set of rear shocks.
 

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Skyking

New Member
Aug 22, 2014
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North Central Texas
Too cool! It definitely needs clip ons.

And what's that tank from? I've been looking for something like that!!
Thanks. I'm having trouble finding the clip-ons. The tubes are only one inch, and the whole triple crown is welded together. So, I have to find a set that not only is abnormally small, but they also need to be a two piece clamp. I may have to just weld a set of bars onto it.
The tank is from an old Garelli. I think these tanks were made by an outside contractor, that makes tanks for several different moped makers. I'm looking for a gas cap now. It's opening is only just a little over an inch.
 
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Skyking

New Member
Aug 22, 2014
106
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North Central Texas
UPDATE: Tires, tubes, and rim strips came today. Mounted, and only one pinch flat. Very soft, and sticky. Should really hold the track, and won't last 500 miles. They're directional. "H" rated. Ambitious? Maybe, maybe not.
Stay tuned............
Oh, and I mounted a better set of rear shocks.
Also; it weighs 47 pounds as shown.
 

Skyking

New Member
Aug 22, 2014
106
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North Central Texas
QUESTION: I need help in deciding what type rear hub to use on this bike. I'm looking at two, and three speed, auto, and kick back shifter, with roller, coaster, and drum brakes. I'm leaning toward either a SRAM, or SA because they offer sealed bearings, and toward the auto shifter because I don't want to worry about what gear I'm in very time is use the roller or coaster brakes.
Please feel free to comment. Remember that this bike has 16" wheels, which will probably affect the shifting speed on the auto shifters.
 

Skyking

New Member
Aug 22, 2014
106
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0
North Central Texas
QUESTION: I need help in deciding what type rear hub to use on this bike. I'm looking at two, and three speed, auto, and kick back shifter, with roller, coaster, and drum brakes. I'm leaning toward either a SRAM, or SA because they offer sealed bearings, and toward the auto shifter because I don't want to worry about what gear I'm in very time is use the roller or coaster brakes.
Please feel free to comment. Remember that this bike has 16" wheels, which will probably affect the shifting speed on the auto shifters.
I went ahead, and bought a set of 16" mag wheels, complete with brakes, sprocket, and axles. They came off of a Tomos moped. They will be in next week.
 

Skyking

New Member
Aug 22, 2014
106
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North Central Texas
Tires remounted onto new wheels. Tires/wheels mounted to bike. Brake and throttle controls hooked up and adjusted.
Tank mounted after the petcock was moved back and down.
Just waiting for the engine mount, transfer case, and BB to arrive.
Oh, and my seat will be ready for pickup the 21st.
 

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Skyking

New Member
Aug 22, 2014
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North Central Texas
Coming along. Got the BB installed. I have the transfer case installed on my GP460 engine. Waiting on the motor mount, and getting my seat back from the upholsterer. Next week, and I may be able to do a couple of shake-down runs. I am so ready to play.
 

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Skyking

New Member
Aug 22, 2014
106
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North Central Texas
Is anyone out there familiar with the Metropolis Patterson crankset, or the Schlumpf crankset. They are both internal 2 speed BB set-ups, and I would love to utilize one if it can be figured out how to apply it to my existing 2 sprocket BB set-up. I lost the ability for adding an internal gear set when I went with the mag wheels, and I would really like to have at least 2 gears on this race bike. I'm pretty sure that I'm going to run out of top end speed before I run out of power with my GP460. I'm going to need another gear.
 
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Skyking

New Member
Aug 22, 2014
106
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North Central Texas
I did some research on the SRAM automatix hub a while back. It's apparently not sealed, and it'll shift on you way too early. With 16" wheels it'll be even worse. This can be fixed though.

http://mccraw.co.uk/sram-automatix-review/

I'm still considering it as an option. I'm just not sure how I can make it look right on my bike.
Thanks green, but that's a rear hub. The two rigs I was talking about are bottom brackets, with internal gears. My wheels are off of a moped. The rear has a internal expanding brake hub on the left side of the mag, and a 22 tooth sprocket on the right side. That set-up is 135mm wide, which leaves me no room for anything else between the rear swing arms.
 

Agreen

Member
Feb 10, 2013
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Well aware! I was referring to your earlier post, which I had missed.

You could still use the hub as a jackshaft I believe. The only concern I have with it is whether it'll hold up to engine abuse. Derailleur shift kits have no problems because they experience such small changes in reduction. The automatix hub goes from 1:1 to 1:1.37, and that's at only 40 rpm (wheel) so if you raise that up to 60 or 80 rpm, that's a big jump and I have concerns that engine torque would eat one of those up. Maybe. It's just a concern.

I've never seen an internally geared bottom bracket. Sounds cool though. I'll have to look in to that some :)
 

Skyking

New Member
Aug 22, 2014
106
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0
North Central Texas
Well aware! I was referring to your earlier post, which I had missed.

You could still use the hub as a jackshaft I believe. The only concern I have with it is whether it'll hold up to engine abuse. Derailleur shift kits have no problems because they experience such small changes in reduction. The automatix hub goes from 1:1 to 1:1.37, and that's at only 40 rpm (wheel) so if you raise that up to 60 or 80 rpm, that's a big jump and I have concerns that engine torque would eat one of those up. Maybe. It's just a concern.

I've never seen an internally geared bottom bracket. Sounds cool though. I'll have to look in to that some :)
I have one of KC Vales new 10G transfer cases with the long shaft that goes to the right side of the mount. So I can't use the jackshaft option. I wish now that I had bought the 4G transfer case so that I could have. When I ordered the unit I had not bought the mag wheels yet.
Yah, the geared BB is pretty cool, but pricey. The Metropolis unit is the cheapest, at around $250 to $300, and the Schlumpf unit is around $400.